Worm press with tapered shaft core

ABSTRACT

The present invention relates to a worm press for separating liquids from solids-liquid mixtures, in particular fibrous suspensions, more particularly under pressure, including a worm rotating inside a jacket comprising liquid passages. The worm press according to the invention is primarily characterized in that the shaft (13) of the worm (14) which is preferably of hollow construction, comprises in the axial conveying direction following onto the region which comprises at least one worm rib (14&#39;), a smooth terminal region (13&#39;) in which the worm shaft (13) is designed as a jacket shaft, provided with a cavity (13&#34;) between a jacket (22) and a preferably hollow core (17), and that this jacket (22) comprises liquid passages, for example bores (3&#34;), leading into the aforementioned cavity (13&#34;), this cavity (13&#34;) being in communication with at least one liquid drainage outlet (18).

BACKGROUND OF THE INVENTION

The present invention relates to a worm press for separating liquidsfrom solids-liquid mixtures, in particular fibrous suspensions, moreparticularly under pressure, including a worm rotating inside a jacketcomprising liquid passages, wherein the shaft of the worm which ispreferably of hollow construction, comprises in the axial conveyingdirection following onto the region which comprises at least one wormrib, a smooth terminal region in which the worm shaft is designed as ajacket shaft, provided with a cavity between a shaft jacket and apreferably hollow shaft core, and that this shaft jacket comprisesliquid passages, for example bores, leading into the aforementionedcavity, this cavity being in communication with at least one liquiddrainage means.

A worm press of the aforesaid type is already known from U.S. Pat. No.3,394,649 (Kemper et al). This worm press serves for the dewatering ofsludges or cellulose pulp suspensions and comprises a hollow worm shafthaving apertures at the end of the pressure zone. Through these boresstill further liquid can be drained into the hollow shaft, this liquiddraining inside the shaft in a direction opposite to the conveyancedirection. However, such a worm press suffers from the disadvantage thatonly small amounts of liquid can be drained through the bores into thecavity of the shaft. Furthermore, these shafts, when employed fordewatering fibrous suspensions are very susceptible to being blocked byfibres.

SUMMARY OF THE INVENTION

Accordingly, it is an object of the invention to provide a worm presswhich is of comparatively simple construction, can be operated at higher(squeezing) pressure which moreover permits a drainage of larger amountsof liquid into the cavity of the shaft and where appropriate alsoreduces the tendency towards blockages by fibres.

This is attained in accordance with the invention in that the cavity inthe terminal region of the worm shaft is formed between a shaft coretapering in the axial conveyance direction and which more particularlyis hollow and the shaft jacket fitted on the former and provided withliquid passages. Due to this tapering terminal region of the worm shafta cross-section which is as large as possible is provided for thedrainage of the liquid. Due to the tapering of the terminal region ofthe shaft, the liquid discharge in the axial conveyance direction ismade possible whereby the liquid pathways can be kept short.

In accordance with a preferred embodiment of the invention, a conveyedmatter retention means, preferably adapted to be regulated is providedin the terminal region of the worm shaft for the purpose of building uppressure in the conveyed material present between the worm and the wormpress jacket surrounding it, outside of the shaft jacket, in particulara pivotable retention flap. Due to the pressure build-up, respectivelythe additional conveyed matter retention means installed in a stationarymanner, the material at the end of the worm press is dammed up, therebybeing subjected to an increased pressure in that region, and liquidstill present in the material being pressed out and discharged throughliquid passages in the jacket of the worm shaft into a cavity.

An advantageous embodiment of the invention is characterised in that theshaft core in the terminal region of the worm shaft conically tapers inthe axial conveyance direction. In that manner the manufacture and theliquid discharge are facilitated.

According to an advantageous embodiment of the invention the liquidpassages in the terminal region of the shaft jacket of the worm shaftare provided in the region of the conveyed material retention means. Inthat manner the liquid discharge can be readily controlled.

Preferably, according to the invention, the liquid passages in theterminal region of the shaft jacket of the worm shaft have across-section which increases towards the cavity between the shaftjacket and the shaft core, i.e. in the direction of discharge of theliquid. The liquid discharge is enhanced thereby.

According to an advantageous embodiment of the invention, partitionsfitted to the shaft jacket of the worm shaft are provided in theterminal region, preferably parallel to the longitudinal axis of theworm shaft and arranged in axial planes, which partitions jointly withthe shaft jacket and the shaft core form channels for the discharge ofthe liquid. This permits the attainment of proper liquid flows.

Expediently at the end of the channels an overflow for the liquid isprovided. According to a further advantageous embodiment of theinvention, rinsing means, preferably spray nozzles, are provided at theend of the channels for cleaning the channels, in particular ofentrained fibres.

Preferably, according to the invention, the worm shaft and also thetapering shaft core fitted thereto are hollow, resulting in a desirableweight reduction of the worm press.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be elucidated by way of example with reference to thedrawings. There is shown in:

FIG. 1 a longitudinal section through a worm press according to theinvention,

FIG. 2 a longitudinal section in the terminal region of the worm press,

FIG. 3 a cross-sectional segment in the terminal region of the wormpress along the plane III--III of FIG. 2 on a smaller scale, and

FIG. 4 a cross-sectional segment in the terminal region of the wormpress along the plane IV--IV of FIG. 2.

DESCRIPTION OF THE PREFERRED EMBODIMENT

In the Figures equal or analogous parts are provided with the samereference numbers: 11 denotes the inlet nipple into the worm chamber, 3denotes the curved screen of the worm chamber and 4 denotes thesupporting body for the screen 3; 13 denotes the shaft, 14' denotes wormfibs on the worm 14, 17 denotes the tapering worm core of the shaft 13;19, 19' denote partitions, 21 denotes retention flaps, 22 denotes theshaft jacket, 23 denotes passages for discharging the liquid and 12denotes a chum at the end of the worm press for discharging thedewatered material.

An overall view of the worm press according to the present invention isillustrated in FIG. 1. The fibrous suspension to be dewatered isintroduced by way of the inlet nipple 11 into the worm chamber. Thischamber is formed, for example of a plurality of successive screens 3 ofcircular curvature forming the cylinder wall and supporting bodies 4.The worm rib(s) 14' of the worm 14 is/are in this context fixed on ahollow shaft 13. Roller axle pins 15 are fitted to the ends of the shaft13, by way of which the shaft 13 (including the worm fib(s) 14', of theworm 14) is rotatably mounted in bearings 16. The dewatered material iseventually discharged through a chute 12 from the worm press. The wormshaft 13 comprises in the terminal region of the worm press a conicallytapering shaft core 17. As also shown in FIG. 3, the shaft core 17, thepartitions 19,19' and the shaft jacket 22, including screen portion 3',jointly form channels 23 for the drainage of the liquid. Finally, theliquid is discharged by way of an overflow 18 from the worm press.

For cleaning the channels 23 rinsing means 20, e.g. spray nozzles areprovided. By means thereof cleaning of the channels may proceed evenwhilst in operation. Previously known embodiments of worm presses oftenhad to be shut down for cleaning purposes and even had to be partlytaken apart.

In order to generate or regulate in the terminal region of the wormpress the pressure required for the separation of the liquid from thesolids suspension, appropriate retention flaps 21 are provided which canbe controlled by way of hydraulic cylinders.

In FIG. 2 a portion of the terminal region of the worm press accordingto the invention is illustrated in longitudinal section. As also shownin FIG. 3, partitions 19,19' are fitted to the shaft jacket 22 andextend radially inwardly to the shaft core 17, or slightly spaced fromthe shaft core 17, in the region of the worm shaft which has the conicaltaper. The partitions 19,19' are substantially planar, and extend inaxial planes parallel to the longitudinal axis of the worm shaft 13. Theshaft core 17, partitions 19, 19' and shaft jacket 22 or the smoothterminal region 13' and portion 3' of the worm shaft form passages 23through which the liquid is drained from the worm press, being separatedfrom solid matter after the passage in the drainage direction 8' throughthe screening section 3' or rather the apertures 3" thereof and throughthe cavity 13" between the smooth terminal region 13' or section 3' andthe shaft core 17. The cavity 13" has a continuously increasing flowcross-section from the apertures 3" to the discharge shute 12. Pressuremay be exercised onto the fibrous suspension to be dewatered by means ofthe controllable retention flap 21.

FIG. 3 shows a cross-sectional segment of the terminal region of theworm press including the individual passages 23 which are formed on theone hand by the walls of the shaft core 17 and the shaft jacket 22 andon the other hand by the partitions 19, 19'.

Finally, FIG. 4 shows a cross-sectional segment in the terminal regionof the worm press including the retention flaps 21 in the region of thesmooth terminal section 13' of the worm shaft for regulating the backpressure or the conveyed material retention such that the materialpresent in this region is subjected to an increased pressure and liquidstill present in the material is pressed out and discharges throughbores 3" in the shaft jacket into the cavity 13" formed by the smoothterminal region 13' and the tapering shaft core 17.

The embodiments illustrated in the Figures serve for explaining theinvention. However, the invention is by no means restricted to theseembodiments.

We claim:
 1. In a worm press for separating liquids from solids-liquidmixtures, including a worm (14) formed as ribs on a shaft for rotationinside a worm jacket (3) having liquid passages, wherein the shaft (13)of the worm (14) includes in the axial conveying direction following atleast one worm rib (14'), a ribless terminal region (13') in which theworm shaft (13) is in the form of a jacket shaft, provided with a cavity(13") between a shaft jacket (22) and a shaft core (17), and this shaftjacket (22) comprises liquid passages (3"), leading into said cavity(13"), said cavity (13") being in fluid communication with at least oneliquid drainage means (18), wherein the improvement is characterized inthat said cavity (13") is formed in said terminal region (13') of theworm shaft (13), between said shaft core (17), which tapers in the axialconveyance direction, and said shaft jacket (22), which is fitted on theshaft and provided with said liquid passages (3"), thereby defining acontinuously increasing flow cross-section in said cavity (13") from theliquid passages (3") to the liquid drainage means.
 2. A worm pressaccording to claim 1, wherein material retention means are providedaround the terminal region (13') of the worm shaft (13) for building upa back pressure in the conveyed material outside of the shaft jacket(22) at said passages (3") leading into the cavity.
 3. A worm pressaccording to claim 2, wherein the liquid passages (3") in the terminalregion (13') of the shaft jacket (22) are provided immediately upstreamof the retention means (21).
 4. A worm press according to claim 3,wherein the liquid passages (3") in the terminal region (13') of theshaft jacket (22) have a cross-section which increases towards thecavity between the shaft jacket (22) and the shaft core (17).
 5. A wormpress according to claim 2, wherein the shaft core (17) tapers conicallyin the terminal region of the worm shaft (13) in the axial conveyancedirection.
 6. A worm press according to claim 2, wherein the materialretention means includes a plurality of adjustable, pivotable retentionflaps.
 7. A worm press according to claim 1 wherein the shaft core (17)tapers conically in the terminal region of the worm shaft (13) in theaxial conveyance direction.
 8. A worm press according to claim 7,wherein the liquid passages (3") in the terminal region (13') of theshaft jacket (22) are provided immediately upstream of the retentionmeans (21).
 9. A worm press according to claim 7, wherein the worm shaft(13) and the tapering shaft core (17) fitted thereto are hollow.
 10. Aworm press according to claim 1, wherein the liquid passages (3") in theterminal region (13') of the shaft jacket (22) have a cross-sectionwhich increases towards the cavity between the shaft jacket (22) and theshaft core (17).
 11. A worm press according to claim 10, whereinpartitions (19,19') fitted to the shaft jacket (22) are provided in theterminal region (13'), parallel to the longitudinal axis of the wormshaft (13) and arranged in axial planes, which partitions (19,19')jointly with the shaft jacket (22) and the shaft core (17) form channels(23) in the cavity for the discharge of the liquid from the cavity tosaid liquid drainage means.
 12. A worm press according to claim 1,wherein the worm shaft (13) and the tapering shaft core (17) fittedthereto are hollow.
 13. In a worm press for separating liquids fromsolids-liquid mixtures, including a worm (14) formed as ribs on a shaftfor rotation inside a worm jacket (3) having liquid passages, whereinthe shaft (13) of the worm (14) includes in the axial conveyingdirection following at least one worm rib (14'), a ribless terminalregion (13') in which the worm shaft (13) is in the form of a jacketshaft, provided with a cavity (13") between a shaft jacket (22) and ashaft core (17), and this shaft jacket (22) comprises liquid passages(3"), leading into said cavity (13"), said cavity (13") being in fluidcommunication with at least one liquid drainage means (18), wherein theimprovement is characterized in thatsaid cavity (13") is formed in saidterminal region (13') of the worm shaft ( 13), between said shaft core,(17), which tapers in the axial conveyance direction, and said shaftjacket (22), which is fitted on the shaft and provided with said liquidpassages (3"), and partitions (19,19') are fitted to the shaft jacket(22) in the terminal region (13'), parallel to the longitudinal axis ofthe worm shaft (13) and arranged in axial planes, whereby the partitions(19,19') jointly with the shaft jacket (22) and the shaft core (17) formchannels (23) in the cavity for the discharge of the liquid from thecavity to said liquid drainage means.
 14. A worm press according toclaim 13, wherein the liquid drainage means are provided at the axialend of the channels (23).
 15. A worm press according to claim 13 whereinrinsing means (20), are provided at the axial end of the channels (23)for cleaning the channels (23) of entrained solids.
 16. The worm pressaccording to claim 15, wherein the rinsing means include a plurality ofspray nozzles.